Finishing varnish for application over lithographic ink



Patented May 27, 1952 if; j j

UNITED STATES PATENT isiiQjjARmsH FORAPPLICATIO OVER'LITHOGRAPHIG INKPaul W. Gre'ubel, Great Nec, Y .,aslsiiiior to American Gan Company, NewYork; N. Yrg'a corporation of New Jersey the hline-graphic ink' printedthereon bfre ppiyin'g thenishig vainisli which constitus; the latingfdperation- Finishing var'nisnes are used 'te 'pieten the nmgfapngastimeend to ip've itsameaancby producing a hard, eietective andgls'synish.

wend navenant advantage@ ifav were cem-mremsn frmufatins", the iminidimc'ulty has 'been inferior appearance such' as'lack of sharpness andlack of gloss in the `finished litliograpliel product.

More Stcjcallyj, @ne inigiofj appearance ,is alle if; offende.' (C1.260x322) nish py/ er 'each of a sries' ef dineren@ inkgfgand also mixingthe 'esitiv inlisj jain d \"/arn'i'si 1esiv and obserying themInicroscopically I` fofun'd 'that in all casesjof failures thereoccurred "alY local. mpvement of the img nlm similar ingactito ofdetergencyj orjWsliing, W335i Vandtlnat' tl'e' 'v ment partfmej'sgoftheimg ruin were ahi/aye;'de-v nqceulated. loseeiammatin revealed thatthe two'nndesirabe'phenoineria, i. e; bl'dir' L# ning andridgingonwaving Vare the same' in p ciple, e`a ch beingI the result of adisturbance r rnoyengent of the' ink as levelling of, the nishingYarnish occnl'sL ]I o folnd that. infaill cases Wherelbleeding andridgingplid not or, tb`r` g.. nient was always iocclilated andv'leejtliese unr desirable phenomenal did occur'tl figment Was'alwaysinastateof deo'ccnlatin.

Upon discovering thek reasbn or caus of the trouble,denocculatio'iijoftn" meinen" jI. started the Search for @properzemedj'. It' oc" curi-get@ megthat the difeulties coulclfpobably beovercome by searhing'outa l' utilizing lithographie inks and nishing' Va'isis Wh`1clfi'a completely orv at leastjslibstantial-lyVinitieiseible'.

I so'on discoyeredthat this anbrdah tothe tic n o f` tile problem was'impractical ifnfvif the'v present Vstate of the art; The' filrn formaterials used in bothinks and yarnishes .are

successful ones, irrespective of their varying chemical composition,ultimately group themselves under a common class which can be defined bytheir common physical characteristics. They must all be liquids. Theymust all be substantially immiscible or at least of a very low order ofmiscibility with the ink vehicle-finishing varnish system. The termimmiscible is used in a relative sense. They must al1 be polarcompounds.

Polar compounds are those in which the force uniting the atoms in thechemical bond is the electrostatic attraction between oppositely chargedparticles. This electrostatic attraction is present in ionizablecompounds and in compounds having electrostatic dissymmetry oroppositely charged groups in their spacial structure.

Immiscible liquids are those wherein one liquid will not blend ordissolve in another or Will blend or dissolve only to a very limiteddegree, such that when they are poured together two distinct or separatelayers or phases result. Absolute immiscibility may be said to benon-existent and may be assumed to be useless as a ilocculant since thiswould imply absolute immiscibility with the other liquids in the Wetvarnish system. Immiscible in connection with the present inventionrefers to a relatively loW order of miscibility in the inkvehicle-finishing varnish system. The force of flocculation induced byimmiscible liquids decreases as miscibility increases.

And finally these materials must be incorporated in the finishingvarnish in certain percentages by weight, which vary with differentvarnish compositions and ink compositions, which percentages will beeffective in inducing immediate ilocculation of the pigment in thelithographic ink.

While immiscibility or substantial immiscibility of the i'locculatingliquids is a necessary characteristic I discovered that because of thelow order of miscibility of these compounds this desirablecharacteristic is accompanied by the phenomenon of sometimesestablishing a twophase system in the finishing varnish. Therefore it issometimes necessary that the immiscible flocculant be renderedsufiiciently accessible to the lithographie pigment, so that it can comeinto intimate contact with said pigment whereby it increases theinterfacial tension between the pigment surface and ink vehicle, whichwill result in immediate, strong iiocculation of the lithographie inkpigment. I solved this problem by introducing a coupling agent or mutualsolvent into the varnish composition. The coupling agent or mutualsolvent must be miscible with the ink vehicle, the varnish vehicle andthe flocculant. The function of the coupling agent or mutual solvent isto maintain the varnish flocculant mixture in a single continuous phasebefore application of the varnish to the inked surface and further tocontinue to maintain a single liquid phase when such mixture is appliedto the wet ink so thatthe flocculant can readily penetrate the inkvehicle layer to gain access to the ink pigment.

Where a certain solvent already in the varnish composition is capable offunctioning as a coupling agent, no additional or a lesser amount ofcoupling agent is required.

Among the flocculants which I have found to be satisfactory are:

(l) Water (2) Alkanols of from l to 3A carbon atoms inclusive such asmethanol, ethanol, isopropanol, normal propanol (3) Lactic acid(commercial U. S. P. grade) (4) Formamide (5) Dihydric alcohols of from2 to 4 carbon atoms inclusive, such as: Ethylene glycol, propyleneglycol, trimethylene glycol, diethylene glycol, etc.

(6) Glycerol For the purpose of the present invention I prefer toemphasize lactic acid (commercial U. S. P. grade).

All of the occulants which I found to be satisfactory, including thosespecifically mentioned come under the definition relatively oilimmiscible, water soluble polar liquids. The word oil in this definitionfor the purpose of my invention means the Water insoluble oil, resin orother film forming materials constituting the vehicle of lithographieinks. My extensive experiments and tests conclusively show that nomaterial or compound which does not come under this definition functionsas a satisfactory ilocculant and conversely all materials or compoundswhich do answer this definition are good flocculants. Lactic acid fallsunder the classification of relatively oil immiscible, water solublepolar liquids.

The lactic acid, with or without coupling agents, is incorporated intothe finishing varnish formulation, in such percentages by weight ofcomplete finishing varnish as will result in the required or optimumflocculation in the Wet ink film.

The percentage of occulant required varies in accordance with theparticular varnish composition in which it is to be embodied. It variesin accordance with the occulating force or ability of the particulariiocculantl itself. And it may vary in accordance with the particularlithographic ink pigment which it is to flocculate. For example, I havefound that Milori Blue requires a higher percentage of occulant thanmany other lithographie ink pigments, and that when bleeding of thispigment is stopped, bleeding etc. of all other pigments also iscontrolled.

The required percentage of fiocculant in each commercial formulation offinishing varnish for stopping either bleeding or ridging can be readilyand quickly determined by the following method.

Bleeding The method consists of preparing several aliquots of a givenvarnish, keeping one aliquot free of ilocculating agent as a control,and adding progressively increasing amounts of flocculating agent ormixture of fiocculants, and coupling agent where necessary, to theremainder. A particular ink is rolled onto a strip of white enameledmetal plate, leaving a sharp, white uninked margin. One strip ofwet-inked plate is dipped (White margin down) into eachvarnishocculating agent mixture, and then allowed to drain. Bleeding, ifpresent, will readily be observed against the background of the whiteenamel.

To determine whether ridging is overcome, `the ascissa preparation offinishing varnish-occulating agent aliquots, and rolling of a particularink on a strip of White enameled'metal plate is identical with theprocedure described under bleeding. However, instead of dipping thestrip of Wet-inked tinplate into the varnish, the varnish is applied'over the Wet ink by means of a roller.v The plate remains iiat at alltimes during this procedure. Ridging, if it occurs, can best be observedby looking at the ink from a 90 degree angle.

I have found that lactic acid is a very effective flocculant inpercentages of from about 3 to 10 per cent, but the practical range(which may be considered the critical range) is wider and extends fromabout 2 per cent to 13 per cent, depending upon the varying factorsheretofore mentioned.

Where a coupling agent or mutual solvent is required, I found that themost satisfactory compounds are those which have a group that islwater-like in character or which may be said to impart Water solublecharacteristics. The most desirable coupling agents all have a freeorganic hydroxyl or alcohol group or an acetylated alcohol group and allcome under the classifications of aliphatic alcohols and glycolmonoethers or acetates thereof. They may be graphically represented byR(O)R' in which R is an aliphatic carbon chain of 4 to 8 carbon atoms ora glycol monoether in which both the glycol and etherv portions of themolecule extend from 2 to 4 carbon atoms and R. is a hydrogen atom or anacetate radical.

The following are suitable as coupling agents either singly or incombination for all my purposes:

which metal decorating finishing varnishes are generally prepared andWith Which the principles of the present invention may be successfullyem-l ployed include:

` A. Polyester polymers ALKYD RESINS Alkyd resins formed by the reactionof polyhydric alcohols and polybasic carboxylic acids and theiranhydrides, modified with non-drying, semi-drying or drying oils, Withor without rosin. with or Without mono or poly-functional phenolicbodies.

78.5% Anya resin solution 60% solids (nim former) 4.8% Lactic acid(occulant) i 6.8% Octanol4 d 6.7% Butano1} Coupling agents 1.0%Lubricant 2.2% Xylene (solvent for lubricant) 65.8% Soya modied alkydresin solution 50% solid (iilm former) 7.9% Lactic acid. (flocculant)26.3% Diethylene glycol monobutyl ether (coupling agent) f v 78.0% Soyamodified oxidizing alkyd solution 50% solids (film former) 5.1% Lacticacid (occulant) pling agents) 7.4% Butanol 1.0% Lubricant 1 r 2.2%Xylene (solvent for lubricant) 59.1% Phenol resinmodiiied alkyd sol.50%" solids (film former) 9.5% Lactic acid (flocculant) 31.4% Diethyleneglycol monobutyl'efther" (coupling agent) POLYMERROF DIBASIC ACID ESTERSOFV UNSATU- ATED MONOHYDRIC ALCOHOLS 27.3% Diallyl phthalate resin(solid) for-mer) 27.3% Diacetone alcohol (resin solvent) 3.3% Lacticacid (ilocculant) 42.1% Acetic ester of diethylene glycol monobutylether" (coupling agent) B. Polyether polymers a ALLYL ETHERs orPoLYHYDRoxY COMPOUNDS 37.3% Auyi staren (solid) (fum former) 32.5%Toluene (resin solvent) 7.4% Lactic acid (Flocculant) 22.8% Diethyleneglycol monobutyl ether (cou-V pling agent) 36.7% Allyl starch (solid)(iilmformer) 31.8% Toluene (resin solvent) 9.1% Lactic acid (flocculant)22.4% Diethylene glycol monobutyl ether (cou-v.l

pling agent) C. Condensation. polymers of aldehydes and amines oralcohols ALKYLATED REACTION PRODUCTS 0F AMINES* AMINE AND AN ALDE- SUCHAS UREA OR MEL HYDE, SUCH AS FORMALDEHYDE 50% solids (film former) 5.7%Lactic acid (occulant) CoNDENsATIoiIoLYMER 0F A RFsIyoUsfAncev ANDALDEHYDE 6.7% Polyvinyl butyral (solid) (film former) 1f 43.2% Butanol(resin solvent) 3.9% Lactic acid (fiocculant) 46.2% Ethylene glycolmonobutyl ether (c oupliiig;

} Coupling agents W (film Resin; solvents 17.6% Vinyl chloride-vinylacetate copolymer (solidi (film: former 30.7% Methyl isobutyl ketone n 426.2 Xylene i Resin` solvents 132% Isopliorone` 7.0% Lactic acid(flocculant) 55.31%, methylene.- gly'col. monobntyl .ether (couplingagent) E. Rosin modified ol'eoresinous 4varnish.

751.4%. Varnish solution701solids` (film former)y 3.1% Lactic acid(ilocculant).` 19.5% Diethylene glycol monooutyl ether (couplingagent)The formulae cited are typical exannrtileszof :my4V invention and manymore could bevadded.

A lubricant-may befIa-dded-to they finishingvarni'shriftllej'sheet;rrletalis to: be ,subjected to f fabricatingp'rocessesfafterI lithograpliing. The addition of the lubricant (whichis optional) Will of4 course. vary the. indicated percentages ofingredients to'a slight degree. Customarily, the lubricant isadded inthe vform of a solution', and the amount added" is regulated so thatthejlubricant solidsare equivalent tov approximately 2 to` 4'percentofthere'sin solidsV in the finishing varnish.

The inclusionl-or exclusiony of a lubricating material has :been .foundto beY- without effect on the pigment fluocculatingability of lacticacid.

The nishing varnish may be prepared Without regardtoxwhethertheenti'relm. formerisy manufactured in a singleoperation, orif Ia ha-rdresin is rst formed' and then combined with ar-dryi'ngaoilin avarnishkettle or ifa solid resin is dissolved in solvents. Further, these'.groups of lm for-mers may be used singly, or in any compatiblecombination, depending on the iilm characteristics" desired.Any/one"skilledv in'v the" art of varnish makingiwill beabletoprepane'the` various varnishes which` maybe used in'connection with mydisclosed invention".v

The above examples are for the purpose-of illustrating-theessentalspiritpof the; present in.- vention; that isltovsay thefinishing varnishis formulated in such amanner asto enable theV same. to.4 induce a1occu'lated;` structure. i'ni the lithographie ink:`

My extensive experiments conclusively indicate that the, nishingvarnishas-covered by the. invention h'ereinbefore describedm'ay 'b'e appliedover any and all wetlith graphicinkscompo'sed of organic and/orinorganic'pi'gments"dispersed" in-`ar-drying 'oi-l'fand-/orA resinEmodied drying' oiland/or other ink'veliicle's suchas are ordinarilyused in lithography, especially metal lithograph'y:

It is thought that-the invention `andmanyfof` its attendant advantages:willbe understood from theiforegoing;description. andlit vvillfbeapparent; that'various changes or modifications may?1 be 75rsisting ofalkyd resins, polyrnerized dib'asicacidgrr'iade'J inthe compositionsdescribed without de4 parting from' the'. spirit' and`r scope of i theinven-4v tin ori sacrificing; all of its material-advantagle'si4 thecompositions lie'reinbefo're'f describedi being4` merely-a preferredenib'o'dixner'it'-tlie'r'eoi.V Y

I4 claim:

LALi'niShingaVarniSh for application over wet'A lithographicfink, ,saidnishingl varnish` ccmprising.. inf. combination, an organicy solventsoluble alkyd resin aszafilm formingsingre'dienty2 to 1'3:

perv cent-by Weight :based on the' nis'hed varnish ofi; anoilimmiscible+waterf soluble' polar: liquid! consisting, ofi lacticAacidA as'v an ink' pigmentfloc-V cularit,Y and avolatileV organicsolventi. for* said.,

resin,l said volatilez solvent.v being: miscible` with the; ink. vehicleand containingv sucientz: coupling agent selected from the groupconsisting-- of' unsubstituted monohydric: alkanols havingfromflftoilfcarbon atoms and glycol monoethers in'V Which-the-glycolportion oi themoleculehas-i from-y 2v to-i 'oarloony-l atoms and'onefree hydroxyly group and the'other hydroxyl-group etherined withanaliphatic hydrocarbon chain havingfz to 4 carbonatoms to maintaintheingredientsin. a-

single liquid -phase.Y

2f. A iinishingvarnishior application'v over Wet lithographie ink', saidfinishing i'larnislfi'V comprising in combination, an. organicsolventsol'ubl syntheticresin selected from the group-consisting ofalkyd resinsg polymerized' di'basic acid.'

gradients, 2 to 13 per cent by Weight based or'i'the" finished varnishof an oil immiscible-Water soluble polar liquid consisting of?. lacticl'acid as. an ink pigment fluocculating agent., and-azvolatile organicsolvent` forA said resins and said-.1 fiocculating agent, said volatilesolvent beingmiscible with ithe link." vehicle andlcontaining-.suffiscientf' unsubstituted monohy'dric alkanol having.

from 4 to 8 carbon atoms as a couplingagent i to maintaintheingredients. in a single. liquidesters of unsaturated monohydricalcohols, res-Y inous polyethers of polyliydr'oxyl compounds,condensation polymers of airlines and aldehydes, condensation polymers of aldehydes and polyvinyl-alcohol, andcopolymersof vinyl' halidesandforganic acidvinyl-esters ras-film fori-ning` Vin5- gredients, 2 to131per cent-by weight'b'ased on the iinished varnish ofv lactic acidiasf an V oil`Y immiscible-Water solubleink pigment floc'culati'ngvagent, and a volatile organic solvent for said resin and saidfiocculating agent, said volatile solvent being miscible With the inkvehicle and containingv suflicient glycol monoether having". i; from 2to 4 carbon atoms in the glycol portion of the molecule andhavingonefreel hydroxyl-- group and the other etheried Withanaliphatichydrocarbon chainv having 2V to'v 4 carbon atoms as coupling agents tomaintain the-,ingredients in a single liquidvphase.

4. A nishing varnish for application over Wet lithographie ink, saidfinishing varnishf comprisingv4 inlcombinationan organicsolvent solublesynthetic resin selected from` the groupe-.co-

9 esters of unsaturated monohydric alcohols, resinous polyethers ofpolyhydroxy compounds, condensation polymers of amines and aldehydes,

condensation polymers of aldehydes and polyvinyl alcohol, and copolymers-of vinyl halides and organic acid vinyl esters as lm formingingredients, 2 to 13 per cent by Weight based on the iinished varnish ofan oil immiscible- Water soluble ink pigment iiocculating agentconsisting of lactic acid, and a volatile organic solvent for said resinand said iiocculating agent. said volatile solvent being miscible withthe ink vehicle and containing suiiicient coupling agent selected fromthe group consisting of unsubstituted monohydric alkanols having from 4to 8 carbon atoms and glycol monoethers having 'from 2 to 4 carbon atomsin the glycol portion of the `molecule and having one free hydroxylgroup and the other etheried with a hydrocarbon substituent having from2 to 4 carbon atoms to maintain the ingredients in a single liquidphase.

5. A method of wet ink varnishing comprising printing a pigmentedlithographie ink on a sheet of web material and occulating the inkpigment by applying over the Wet ink a finishing varnish containing anorganic solvent soluble film forming resin dissolved in a volatileorganic solvent that is miscible with the ink vehicle, 2 to 13 per centby weight based on the finished varnish of an oil immiscible-Watersoluble pigment iiocculating agent consisting of lactic acid, andsufficient coupling agent selected from the group consisting ofunsubstituted monohydric alkanols having from 4 to 8 carbon atoms andglycol monoethers having from 2 to 4 carbon atoms in the glycol portionof the molecule and having one free hydroxyl group and the otherhydroxyl group etheriiied with a hydrocarbon substituent having from 2to 4 carbon atoms to maintain the varnish in a single liquid phase.

6. The methods of claim 5 in which the resin is selected from the groupconsisting of alkyd resins, polymerized disbasic' acid esters ofunsaturated monohydric alkanols, resinous polyethers of polyhydroxycompounds, condensation polymers of aldehydes and amines, condensationpolymers of polyvinyl alcohol and aldehydes, and copolymers of vinylhalides and organic acid vinyl esters.

7. The method of claim 5 in which the resin is a synthetic resin solublein a volatile organic l solvent.

8. The method of claim 7 in which the resin is formed by polymerizationof a compound containing a vinyl group.

9. The method of claim 7 in which the resin is a condensation polymer ofamines and aldehydes.

10. The method of claim 7 in which the resin is an alkyd resin.

11. The method of claim 5 in which the web material is a metal sheet.

12. The method of claim 11 in which the metal sheet is tin plate.

13. The method of claim 11 in which the metal plate is steel.

14. The method of claim 5 in which the coupling agent is anunsubstituted alkanol having from 4 to 8 carbon atoms.

15. The method of claim 5 in which the coupling agent is a glycolmonoether having from 2 to 4 carbon atoms in the ether portion of themolecule and having one free hydroxyl groupv and the other hydroxylgroups etheried with a hydrocarbon substituent having from 2 to 4 carbonatoms.

16. A finishing varnish for application over wet lithographie ink, saidnishing varnish comprising in combination an organic solvent solubleresinous polyether of polyhydroxy polymeric compounds as a nlm formingingredient. 2 to 13 per cent by weight based on the finished varnish ofan oil immiscible, Water soluble polar liquid, consisting of lactic acidas an ink pigment flocculant, and a volatile organic solvent for saidingredient, said volatile solvent being miscible with the ink vehicleand containing suicient coupling agent selected from the groupconsisting of unsubstituted monohydric alkanols having from 4 to 8carbon atoms and glycol monoethers in which the glycol portion of themolecule has from 2 to 4 carbon atoms and one free hydroxyl group andthe other hydroxyl group etheried with an aliphatic hydrocarbonsubstituent having from 2 to 4 carbon atoms, to maintain the ingredientsin a single liquid phase.

17. A iinishing varnish for application over wet lithographie ink, saidiinishing varnish comprising in combination, an organic solvent solubleresinous condensation polymer of an amine and an aldehyde as a lmforming ingredient, 2 to 13 per cent by weight based on the finishedvarnish of an oil immiscible-water soluble, polar liquid, consisting oflactic acid as an ink pigment iiocculant, and a volatile organic solventfor said ingredient, said volatile solvent being miscible With the inkvehicle and containing suiiicient coupling agent selected from the groupconsisting of unsubstituted monohydric alkanols having from 4 to 8carbon atoms and glycol monoethers in Which the glycol portion of themolecule has from 2 to 4 carbon atoms and one free hydroxyl group andthe other hydroxyl group etheried with an aliphatic hydrocarbonsubstituent having from 2 to 4 carbon atoms, to maintain the ingredientsin a single liquid phase.

18. A nishing varnish for application over Wet lithographie ink, saidnishing varnish comprising in combination an organic solvent solubleresinous copolymer of a vinyl halide and an organic acid vinyl ester asa iilm forming ingredient, 2 to 13 per cent by Weight based on theiinished varnish of an oil immiscible-Water soluble, polar liquid,consisting Vof lactic acid as an ink pigment iiocculant, and a Volatileorganic solvent for said copolymers, said volatile solvent beingmiscible with the ink vehicle and containing suiiicient coupling agentselected from the group consisting of unsubstituted monohydric alkanolshaving from 4 to 8 carbon atoms and glycol monoethers in which theglycol portion of the molecule has from 2 to 4 carbon atoms and one freehydroxyl group and the other hydroxyl group etheried with an aliphatichydrocarbon substituent having from 2 to 4 carbon atoms to maintain theingredientsin a single liquid phase.

PAUL W. GREUBEL.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,174,012 Saunders Sept. 26, 19392,423,872 Clipper July 15, 1947

1. A FINISHING VARNISH FOR APPLICATION OVER WET LITHOGRAPHIC INK, SAIDFINISHING VARNISH COMPRISING IN COMBINATION, AN ORGANIC SOLVENT SOLUBLEALKYD RESIN AS A FILM FORMING INGREDIENT, 2 TO 13 PER CENT BY WEIGHTBASED ON THE FINISHED VARNISH OF AN OIL IMMISCIBLE-WATER SOLUBLE POLARLIQUID CONSISTING OF LACTIC ACID AS AN INK PIGMENT FLOCCULANT, AND AVOLATILE ORGANIC SOLVENT FOR SAID RESIN, SAID VOLATILE SOLVENT BEINGMISCIBLE WITH THE INK VEHICLE AND CONTAINING SUFFICIENT COUPLING AGENTSELECTED FROM THE GROUP CONSISTING OF UNSUBSTITUTED MONOHYDRIC ALKANOLSHAVING FROM 4 TO 8 CARBON ATOMS AND GLYCOL MONOETHERS IN WHICH THEGLYCOL PORTION OF THE MOLECULE HAS FROM 2 TO 4 CARBON ATOMS AND ONE FREEHYDROXYL GROUP AND THE OTHER HYDROXYL GROUP ETHERIFIED WITH AN ALIPHATICHYDROCARBON CHAIN HAVING 2 TO 4 CARBON ATOMS TO MAINTAIN THE INGREDIENTSIN A SINGLE LIQUID PHASE.